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Cummins X15 CM2450 X124B (2018 & Newer) Fault Code: 755 PID: PID 157 SPN: 157 FMI: 7 Injector Metering Rail 1 Pressure- Mechanical System Not Responding or Out of Adjustment

Circuit Description
The engine control module (ECM) provides a 5 volt supply to the fuel rail pressure sensor using a dedicated sensor supply circuit. The ECM also provides a ground on the sensor return circuit. The fuel rail pressure sensor provides a primary fuel pressure signal to the ECM on the fuel rail pressure sensor signal 1 circuit. The sensor also provides a secondary fuel pressure sensor signal on the fuel rail pressure signal 2 circuit. This sensor signal voltage changes based on the pressure in the fuel rail. The ECM will detect a high signal voltage at high rail pressure conditions. The ECM will detect a low signal voltage during low rail pressure conditions.

Component Location
The high-pressure fuel pump is mounted to the gear housing. The fuel pump actuator is mounted on the fuel pump. The fuel pressure sensor is mounted in the high pressure fuel rail. The fuel pressure relief valve is mounted on the high pressure fuel rail.

Conditions for Running the Diagnostics
The second part runs continuously while the engine is running.
Conditions for Setting the Fault Codes
The Engine Control Module (ECM) detected the difference between the fuel rail 1 pressure signal and the fuel rail 2 pressure signal was greater than a threshold for 2 consecutive trips.

Action Taken When the Fault Code is Active
The ECM illuminates the amber CHECK ENGINE lamp and/or Malfunction Indicator Lamp (MIL) after the diagnostic fails on two consecutive trips.

A default value for the fuel rail pressure reading is used.
Exhaust Gas Recirculation (EGR) valve operation will be disabled.
Engine torque will be reduced if the engine is operated for an extended period of time with this fault active.
Conditions for Clearing the Fault Code
To validate the repair, start the engine and let it idle for up to 5 minutes.
The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after three consecutive trips where the diagnostic runs and passes.
The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop Talk
Possible causes of this fault code include:

A malfunctioning fuel rail pressure sensor

Possible Cause:
1) ECM failure